all: change module to google.golang.org/protobuf

Temporarily remove go.mod, since we can't generate an accurate one until
the corresponding v1 change is submitted.

Change-Id: I1e1ad97f2b455e33f61ffaeb8676289795e47e72
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/177000
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/internal/encoding/defval/default.go b/internal/encoding/defval/default.go
index e2c62a9..a15df02 100644
--- a/internal/encoding/defval/default.go
+++ b/internal/encoding/defval/default.go
@@ -14,9 +14,9 @@
 	"math"
 	"strconv"
 
-	ptext "github.com/golang/protobuf/v2/internal/encoding/text"
-	errors "github.com/golang/protobuf/v2/internal/errors"
-	pref "github.com/golang/protobuf/v2/reflect/protoreflect"
+	ptext "google.golang.org/protobuf/internal/encoding/text"
+	errors "google.golang.org/protobuf/internal/errors"
+	pref "google.golang.org/protobuf/reflect/protoreflect"
 )
 
 // Format is the serialization format used to represent the default value.